<!DOCTYPE html>
<html>
<body onload="setup()">
<textarea id="ta" dir="rtl">

&#x05d0;a&#x05d1;

</textarea>
<textarea id="tb">

abc

</textarea>

<div id="coords1"></div>
<div id="coords2"></div>

<script>
  function setup() {
    document.getElementById("ta").selectionStart = 3;
    document.getElementById("ta").selectionEnd = 3;
    document.getElementById("coords1").innerHTML = document.getElementById("ta").selectionStart;
    document.getElementById("tb").selectionStart = 3;
    document.getElementById("tb").selectionEnd = 3;
    document.getElementById("coords2").innerHTML = document.getElementById("tb").selectionStart;
  }
</script>
</body>
</html>
